This invention relates generally to valves, and more particularly to a novel sealing arrangement or sealing member for a valve.
Of particular interest in the design of valves and valve components is the design of the sealing members and sealing arrangements employed therewith. In this regard, valve designers continually strive to provide a relatively simple and inexpensive, yet highly reliable, sealing arrangement. In valves designed to accommodate fluids at relatively high pressures and/or temperatures, the service life and reliability of the sealing arrangement is of particular importance, and as such new, improved designs are continually sought.
Examples of novel approaches in effecting a simple yet reliable sealing arrangement are shown in the inventor's prior U.S. Pat. Nos. 3,563,510 and 4,044,994. While these arrangements have proven highly effective in a number of applications, the present invention contemplates a novel alternative thereto which provides certain additional advantages and improvements not heretofore obtainable.
Among the factors to be taken into consideration in the design and construction of a valve sealing arrangement are the range of pressures and temperatures which the valve is to be designed to handle, and the basic design of the valve itself. In the latter regard, a valve construction employing a relatively movable flow control member against which the seal must engage, as utilized in a ball, disc, or butterfly types of valves, requires a relatively rugged sealing member. In addition, relatively soft, elastic or elastomeric materials are generally inadequate for sealing in valves which are intended to handle fluids at relatively high pressures and/or temperatures. Accordingly, in uses of this type it is necessary to employ a degree of rigidity or strength in the sealing material, as well as wear resistance to the abrasion resulting from engagement with the flow control member and also solid particles or abrasives in the fluid being transported through the valve.
The sealing member must, however, be capable of attaining effective initial sealing contact, as well as final sealing contact. That is, an operational seal must be maintained between the seal and opposed sealing surface at low line pressures or prior to the time when line pressure is applied to the closed valve structure, as well as in high line pressure situations. On the other hand, the sealing member and arrangement must be possessed of a sufficient degree of elasticity to accommodate the resulting slight movement of the control member under the influence of line pressure. In this regard, the sealing member and arrangement must be capable of elastic movement or deflection to some degree to assure continued effective sealing with the sealing surface, as the point of sealing engagement may change somewhat due to the pressure loading and movement of the flow control member. Moreover, such elasticity of the sealing member and arrangement must be such as to substantially preclude any detrimental permanent deformation thereof, which would tend to render the seal ineffective.
It has been proposed and is known in the art to employ resilient metal seals for high temperature, and/or high pressure applications. However, where the valve and seal must also handle abrasive fluid mixtures, additional problems are encountered. More specifically, while relatively thin metal seals are sufficiently resilient to provide the desired sealing action, they will soon be eroded by the abrasive material. Accordingly, to prevent this erosion, the tendency is to fabricate the seal from a thicker material. With the thicker materials, there is a problem due to lack of resiliency. The present invention, however, overcomes these prior art problems, in that it is sufficiently resilient to provide the desired sealing action, yet is resistant to erosion.
More specifically, with a flexible seal wherein one end thereof is anchored and the intermediate section is relatively rigid, flexing of the seal produces an uneven loading of the seal with the greatest moment occuring at the point of attachment of the seal to the anchored segment. This creates an undesirable stress pattern which can result in permanent deformation and premature failure of the seal. With the present invention, two solutions to this problem are shown, in the first, the seal or sealing member is generally in the form of a folded beam, with the cross section of the seal selected to provide approximately uniform stress or loading. More specifically the cross section of the "beam" which defines the seal is diminishing from the point of fixed connection toward the point of contact with the flow control member. The various cross sectional dimensions, which can be determined using well-known formulas for beams wirh uniform stress, are selected so that the stress in the seal convolutions is approximately constant when the seal is deflected axially by the flow control member. It should be noted that it is this axial deflection that produces the beam type loading. In a second form of the invention, the seal includes a relatively massive, sealing portion in the form of a rigid annular seal or seat ring. The ring is joined to the base section of the overall seal assembly by a relatively thin intermediate section which is corrugated in the axial direction. This design permits the seat ring to move in both the radial and axial directions. More specifically, slight radial movement is provided to permit the seat ring to adjust its radial position to conform to that of the flow control member; further, the seat ring can deflect axially upon engagement with the flow control member. Since the intermediate section in this embodiment is more flexible in the axial direction in order to obtain firm sealing contact with the flow control member, an axially directed biasing force is provided by a spring carried within the seal groove. The spring is preferably in the form of an annular wave spring which may be separate or joined to the overall assembly.
In accordance with the above, the present invention includes a sealing member for a valve of the type including a flow control member and an annular sealing surface. Said annular sealing member has an end portion confronting the sealing surface, and in cross section is convoluted so as to resemble a plurality of corrugations. In one form, the thickness of the seal member segments which define said convolutions decreases in the direction toward the free end of the sealing member. The cross sectional dimensions are selected to simulate a beam of uniform stress, thereby substantially evenly distributing stress throughout the sealing member during engagement with said sealing surface. In a second form, a solid sealing ring is used in conjunction with a corrugated intermediate section, with a wave spring biasing the seal ring axially toward the flow control member.
A valve arrangement in accordance with the invention, and embodying the sealing member, comprises a first element constituting a valve body and defining a flow passage extending therethrough, a second element constituting a flow control member movably supported relative to said body for opening and closing said flow passage, one of said elements defining an annular sealing surface and the other of said elements defining an annular sealing member support groove oriented to confront said sealing surface, said annular sealing member being disposed in said support groove and having a first segment fixedly anchored in said support groove and a second segment extending radially inwardly thereof. The second segment includes a free or opposite end which confronts the sealing surface for engagement therewith. The dimension of the support groove is sufficiently large to permit axial deflection of the second segment. As an additional feature, said second segment includes one or more corrugations that also permits the seal to be compressed radially. The resiliency of the seal member, i.e. its tendency to return to its original position serving to effect a fluid tight seal.